An air conditioner is an apparatus for cooling/heating an indoor space or purifying air in order to provide a more pleasant indoor environment.
Such air conditioners are classified into a separation type air conditioner, in which an indoor unit and an outdoor unit are separate from each other, and an integrated air conditioner, in which an indoor unit and an outdoor unit are integrated. Air conditioners may also be classified, in accordance with capacities thereof, into a single type air conditioner, which has a capacity to drive one indoor unit, for use in a small space, a large-size air conditioner, which has a great capacity, for use in companies or restaurants, and a multi-air conditioner, which has a capacity to sufficiently drive a plurality of indoor units.
The separation type air conditioner includes an indoor unit installed in an indoor space, to supply hot air or cold air to the indoor space, and an outdoor unit for executing compression, expansion, etc. of refrigerant in order to enable the indoor unit to perform effective heat exchange operation.
Meanwhile, air conditioners may also be classified, in accordance with power sources for driving a compressor, into an EHP type air conditioner and a GHP type air conditioner. The EHP system uses electricity as a power source for a compressor, whereas the GHP system uses fuel such as liquefied natural gas (LNG) or liquefied petroleum gas (LPG). In the GHP system, an engine operates through combustion of fuel, to provide power for a compressor motor.
The EHP system has advantages in that it is possible to appropriately cope with partial load while achieving high energy efficiency because easy compressor control is possible through adjustment of supply current. However, the EHP system has a problem in that frost may be formed on an outdoor heat exchanger during low-temperature heating.
On the other hand, the GHP type air conditioner has an advantage of excellent defrost performance through utilization of waste engine heat. However, there is a problem of low engine efficiency due to heat loss, etc.